Platform structure

ABSTRACT

A roof platform or deck structure consists of a plurality of elongated prefabricated reinforced-concrete elements of invertedU or cross-section interconnected contiguously and independently self-supporting so that the structure is self-supporting when formed without the need to cast concrete in place. The individual elements are formed in a mold having a removable inner member which remains in place after withdrawal of the partially hardened concrete body until the latter becomes at least self-supporting.

United States Patent [1 1 Haller et al.

[ Oct. 23, 1973 PLATFORM STRUCTURE Inventors: Hans Haller; Erwin Wendi, both of Nibelungengasse 40, Graz, Austria Filed: Sept. 28, 1970 Appl. No.: 75,851

3,303,545 2/1967 Heitzman 25/41 J 3,030,688 4/1962 Tumey 249/79 X 3,132,403 5/1964 Richards et al 249/50 Priniary ExaminerJ. Spencer Overholser Assistant Examiner-Dewalden W. Jones Att0meyl(arl F. Ross [30] Foreign Application Priority Data ABSTRACT Sept. 23, 1969 Austria A 9016/69 A roof platform or deck structure consists of a plurality of elongated prefabricated reinforced-concrete ele- [52] U.S. Cl. .t 249/18, 249/79 ments of inverted-U or cross-section interconnected [51] E04g 11/00 contiguously and independently self-supporting so that [58] Field 01 Search 249/18, 26, 28, 31, the structure is self-supporting when formed without 249/32, 50,79, 142, 144, 155, 177, 176; the need to cast concrete in place. The individual ele- 25/41 J ments are formed in a mold having a removable inner member which remains in place after withdrawal of [56] References Cited the partially hardened concrete body until the latter UNITED STATES PATENTS becomes at least self-supporting. 1,729,001 9/1929 Lancrenon 249/144 X 10 Claims, 10 Drawing Figures 204- 0L Z7 7 K 20a a V Qoooooooooop 6 g. 22 3 2-' o a o 36 :1-

Patented Oct. 23, 1973 3,767,153

3 Sheets-Shout 2 2 I VIBRATORS 8 9 Hans Hal/er Erwin Wen d/ Inventors.

By g? M Attorney Patented Oct. 23,1973 7 3,767,153

3 Sho0ts5hoot 5 AK A )Mk Hans Hal/er Erwin Wendi lnvenfors.

{Kai Attorney PLATFORM STRUCTURE FIELD OF THE INVENTION Our present invention relates to concrete roof, platform or deck structures, to an improved method of making such structures and, more particularly, to molds for producing the elements constituting such structures.

BACKGROUND OF THE INVENTION In the manufacture of concrete roofs, platforms or decks it has been the practice heretofore to provide a plurality of spaced-apart beams onto and about which is cast concrete with the aid of a formwork or the like. Upon removal of the formwork, the roof, platform or deck is self-supporting and constitutes a substantially monolithic structure. Concrete roofs, platforms or decks have also been made by casting a slab of concrete in place between the supports to create a monolithic structure. Neither of these two systems has proved to be entirely satisfactory. When beams have been used, for example, it has been the practice to dimension them to be as small as possible, thereby limiting the span of the beamsand the size of the roof, platform or deck structure to be produced therefrom. Both systems have, moveover, been found to be relatively expensive, in no small part on account of the requirement that they be cast in situ. The casting of the roof, platform or deck structure elsewhere and its transportation to the erection site also is no solution because of the high cost.

OBJECTS OF THE INVENTION It is the principal object of the present invention, therefore, to provide improved means for making a concrete roof, platform or deck structure designed to eliminate the need for hardening wet concrete in situ.

A more particular object of the invention is to provide an improved mold for the production of the structural elements of a concrete roof, platform or deck.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, in a roof, platform or deck structure spanning a pair of spaced-apart supports and composed of laterally contiguously elongated concrete structural elements of substantially identical configuration which are entirely self-supporting and unitarily span the supports, the elements being laterally connected to produce a roof, platform structure or deck having substantially the characteristics and strength of a monolithic concrete slab or shell, or stress and strength characteristics exceeding those of a precast or reinforced concrete shell.

Our invention is based upon the discovery that the individual elements of the structure, which are entirely self-supporting between-the horizontally spaced support members, can be coupled together in a laterally contiguous relationship, so as to define a substantially continuous roof, platform or deck surface without the application of wet concrete or the pouring, casting or other application of concrete in situ.

Advantageously, each of the individual elements of such a structure has an inverted'U cross-section with a web lying along the bight of the U and a pair of flanges corresponding to the legs thereof. Our invention is also width of the laterally projecting marginal portion of the web. The wall thickness of the flanges is 4-5 cm.

Best results are obtained when the flanges converge or diminish in thickness downwardly, i.e., when the channel defined by the element is approximately of trapezoidal cross-section with the narrow base of the trapezoid at the web and the broad base of the trapezoid between the free ends of the flanges. The convergence of the flanks of the flanges provides no structural disadvantage and indeed reduces the weight of the elements without materially limiting their load-carrying capacity and furthermore provides a draft facilitating the withdrawal of the cast concrete elements from the mold.

According to basic aspect of the invention, we provde a mold for the formation of the structural elements which comprises an upwardly open outer shell and an inner shell conforming substantially to theme cess or cavity of the structural element which is removably received in the outer shell and defines therewith a channel-like mold cavity of invertedll org corjiguratiofiTThe concrete is cast in this cavity, preferably after the introduction of the reinforcing members into the latter, and is compacted and vibrated (jarred or jolted) by vibrating members affixed to the outer shell. According to an important feature of the invention, the non-self-supporting and only partially hardened concrete body is lifted from the outer shell of the mold upon the removable inner shell and permitted to set upon the latter while a fresh inner shell is introduced into the mold for the casting of a further structural element thereon. Once the soft concrete has hardened, e.g., to a point at which the concrete body is self supporting, the inner shell can be removed.

Hence the inner form of the double-form mold has several functions. Firstly, it constitutes the inner wall defining the web and flanges of the structural element. Secondly, it constitutes a support and transport frame or bed for the cast but unhardened concrete. Thirdly, it may constitute a means for facilitating the hardening of the concrete. Furthermore, since only the outer shell need be provided with vibrators, the production of the concrete bodies can proceed with limited capital expenditure and no obstruction of the casting and jolting operation during the hardening of the concrete bodies. The system of the present invention has the further advantage that the moist concrete bodies, prior to complete setting, may be subjected to further treatment outside the mold at locations which would be inaccessible on bodies within the mold. Such operations may include the formation of openings within the body to permit the introduction of transverse supports or fastening means.

In order to expedite the removal of the cast concrete bodies prior to complete hardening, the ends of the mold cavity defined by a pair of end plates fixed to the inner shell may be provided with means, e.g., wire loops, cutouts or the like, engageable by the hooks of a crane. Furthermore, since the load-carrying capacity of the platform and the ability of its constituent elements to span large distances depends upon the height of the flanges, we provide means in the mold for adjusting the flange height to the construction conditions. Such means may include insert strips raising the floor of the mold and thereby foreshortening the depths of the mold cavity, such strips preferably being adjustably mounted upon the inner shell. Similarly, we may use a single mold for the production of elongated structural elements of different length in accordance with the above principles, in which case we subdivide the mold longitudinally with templates having the configuration of the desired cross-section of the structural element and forming the ends of individual mold compartments. Such templates fit within the mold cavity and advantageously serve as patterns for the adjustable walls of the cavity to enable the latter to be readily positioned for a particular cross-section of the structural elements. The templates may be provided with fastening means for mounting them at any desired locaction along the mold walls, advantageously upon the outer form. Furthermore, the templates can impart the desired terminal angle to the structural elements and may be provided with a mold surface of corresponding configuration.

According to another feature of the invention, the hardening of the concrete upon the inner form is accelerated by conducting a heating medium through the latter. Advantageously, this heating is accomplished after the removal of the inner form from the mold and a number of such inner forms can be positioned at the setting station to conduct the heating medium, e.g., steam or hot air, therethrough.

The inner form can be made from sheet metal, this material having been found to be particularly satisfactory when heating of the concrete body from within is desired. Since a number of such inner forms is required, however, and it may be desired to make inner forms associated with each flange height, we may cast the inner forms from concrete and especially lightweight concrete having aggregates of expanded mineral. It has been found to be advantageous, in all cases in which a concrete inner from is used, to provide it with a highly smooth surface of, for example, a synthetic resin. In the preferred case, however, an adjustable inner form is employed and, when a cast inner form is used, it is provided in its interior with conduits for the heating medium. When a qr-shaped body is to be produced, moreover, it has been found to be advantageous to employ a number of removable inner forms. The inner forms can include a pair of outer members having a cross-section corresponding approximately to half that of the central member. The several inner forms may be connected together by plates, e.g., a bottom plate spanning the floor of the outer form and/or endplates closing the extremities of the mold cavity. The connecting plates may be provided with means enabling the crane to grip the forms and the concrete body carried thereby. In this case also, the spacer templates must have legs conforming to the rr-shape and extending between the inner forms.

BRIEF DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a perspective view of a roof, platform or deck structure, made in accordance with the present invention, as seen from above;

FIG. 2 is a perspective view of the structure as seen from below;

FIG. 3 is a side-elevational view of a mold for the production of the structural elements used in the roof, platform or deck structure of FIGS. 1 and 2;

FIG. 4 is a plan view of the mold of FIG. 3;

FIG. 5 is a detail end view, partly in diagrammatic form, of a mold for producing structural elements having an inverted-U cross-section according to the invention;

FIG. 6 is an elevational view of a template for use in the mold of FIG. 5;

FIG. 7 is an elevational view of a strike board for use with the mold of FIG. 5 or the mold of FIGS. 8 or 9;

FIG. 8 is a vertical section through another mold according to the invention;

FIG. 9 is an end view of a mold for producing still another structural element according to the invention; and

FIG. 10 is a view of the template of FIG. 6 in side elevation.

SPECIFIC DESCRIPTION In FIGS. 1 and 2 of the drawing, we have shown a basic roof, platform or deck structure spanning a pair of supports 27 and 26 that are horizontally spaced apart.

The support 26 is shown to be a grate or the like forming a wall into which the far ends of the structural elements constituting the roof, platform or deck extend to be embedded or cemented with mortar or concrete. The support 27 merely forms a masonry pillar upon which the roof structure rests. It should be understood that the invention is applicable to any type of support structure so that either support may be secured by cement, bolts, flanges or the like to the structural elements, or may be of the kind upon which the roof, platform or deck rests via a ledge, shoulder or other horizontally disposed surface.

The roof, platform or deck structure comprises a plurality of laterally contiguous substantially identical structural elements of channel configuration, the elements being represented generally at 20. The elements are of inverted-U cross-section; while structurally different elements have been shown in these Figures, it will be understood that the roof, platform or deck structure will generally consist of elements of only one kind. Each of the elements, however, comprises a horizontal web 21, forming the bight of an inverted-U, and, monolithic, integral and in one piece therewith, a pair of longitudinally extending flanges 22 lying in vertical planes.

Each of the structural elements 20 has a length L sufficient to span the distance D between the supports 26 and 27 and a width w which is a minor fraction of the length L. In general, the length may be ten times the width or more. The width w corresponds to the bight of the channel; the web has a thickness t, of 3 to 10cm while the flanges 20 have a thickness 1 of approximately 4 or 5cm. The structural element 20a (FIG. 2) is shown to have a reinforcement 20a in the form of a mat, grid or mesh bent into channel configuration and extending both along the web 21 of the structural element and within the flanges 22 thereof.

The element b, however, is seen to be formed with a reinforcement as constituted by arrays of reinforcement bars which may be transversely interconnected by stirrups (now shown) in accordance with conventional techniques. Tie rods traverse the flanges 22 of the structural elements in the transverse direction and are tightened at the lateral ends of the roof structure via, for example, nuts 31 (FIG. 1) to hold the longitudinal edges 20c of the contiguous structural elements 20, 20a, 20b etc. together to form an uninterrupted roof surface.

Alternatively, each pair of adjoining members can be coupled together by bolts 32 traversing the respective flanges 22. It has also been found to be advantageous to laterally interconnect the elements by members extending through the webs 21 as represented diagrammatically at 33, access to the bolts being afforded by openings 23 provided in these webs. Additional openings 24 can be formed in the flanges 22 to accommo date the tie rods 30, and transversely extending ribs 25 of a profile resembling that of the flanges 22 may bridge the flanges at longitudinally spaced locations (FIG. 2).

At one or more locations along the lower surfaces 22a of the flanges, we may provide pins or studs to which ceiling structures in the form of insulating plates 34 may be affixed. The attachment'of the insulating members 34 may be accomplished as well by affixing synthetic resin or wood strips 36 to the lower edges of the flanges by positioning these strips in the mold and providing them with projections 37 which are embedded in the concrete.

The openings 23 and 24 may, in part, be formed by inserts 38 of wood or foamed synthetic resin (e.g., cellular polystyrene) which can be extracted from the molded member prior to erection of the roof. In FIG.

2, one such knockout is shown in place at 38. The openings 23 may also be conveniently employed to insert transverse supports 39 having footings 40 which bear against the oppositely facing inner surfaces of the flanges 22 to strengthen the structure against the inward force applied by the tie rods 30. The strips 36, of course, permit the members 35 tobe mounted on the concrete roof by nailing, stapling or the like. The structure illustrated in FIGS. 1 and 2, whether produced by lateral tensioning of a support carrying the loosely disposed but contiguous members 20 or by tying the members together in pairs or in groups as previously described, yields a stiff plate which is self-supporting. No application of web concrete in situ is required and the plate has the structural characteristics of a monolithic slab. It is possible to walk upon it immediately after its erection. The tie rods 30 may be encased in concrete concurrently with the formation of webs similar to that shown at 25 and openings 23 and 24 may be closed by surrounding the indicated portions with falsework and pouring concrete through the openings 23, the concrete lying flush with the upper surface of the deck.

In FIG. 5, we show an outline (broken lines) of the actual cross-section of the inverted U or channelshaped members produced in accordance with the present invention and diagrammatically illustrated at 20 in FIGS. 1 and 2. From this Figure it will be apparent that the inner flanks of the flanges 22 preferably diverge downwardly with a slight draft so that the space within the channel has the configuration of a trapezoid, the broad base of which is defined by a line connecting the free ends of the flanges 22 while the narrow base lies along the web 21. As shown in FIG. 9 in broken lines, the outer flanks of the flanges may converge toward the inner flanks so that the flanges taper downwardly in cross-section and are of reduced thickness remote from the web 21.

In FIGS. 3 5 and 9, we have shown molds for producing structural elements in accordance with the present invention. These molds comprise a pair of outer walls 2a and 2b which define the flanks of the concrete element and form a chamber 40 between them into which the concrete may be cast. The walls 20 and 2b extend continuously over the entire length of the form, which equals the maximum length of a concrete element to be produced by the system. The walls 2a and 2b are affixed by bolts 41 to spaced-apart brackets 42 consisting of upright arms 42a, carrying the walls 20 and 2b, and horizontal arms 42b provided with slots 42c running transversely to the major dimension of the form. Reinforcing ribs 42d interconnect the arms to stiffen the brackets.

As further shown in FIG. 5, the brackets 42 are mounted upon spaced'apart I-beams 1 anchored at In to a foundation, e.g., a concrete footing and provided with centering screws 7 for proper alignment of the lbeams and, therefore, of the formwork. Bolts 14 pass through the slots 42c and into the upper flange of the I-beam 1 to adjustably anchor the brackets 42 thereto. By loosening the nuts of these bolts, it is possible to move the brackets 42 inwardly or outwardly and thereby change the width w of the concrete element to be formed in the mold. The upper edge 20 of each wall 20, 2b extends continuously above the brackets 42 and thereby serves as a guide for a strike bar, e.g., as shown at 15 in FIG. 7. Generally, however, the strike bar will merely be a board whose underside rests upon the guide edges 20 to strike the concrete flush with these edges.

Apart from the outer formwork generally designated 2, we provide an inner form or core generally indicated at 3 and preferably composed of synthetic resin. The form 3 is wholly removable from the outer form 2 by a crane or the like in a manner not illustrated. The form 3 may also be composed of concrete, wood or sheet metal and may be designed for a particular configuration or may be adjustable to suit any configuration and dimensions of the mold cavity 40.

More particularly, the inner mold may be spanned by a pair of bars 9 in the longitudinal direction, the bars 9 extending beyond the ends of the mold cavity at 9a and 9b as shown in FIG. 4 to enable the hooks of the crane to engage the inner form and lift it, together with the concrete body cast therearound, from the outer form 2. A sheet-metal horizontal member 3a forms the roof of the inner form 3 and has, preferably, a symmetrically downward camber from a central crest as best seen in FIG. 5. The inner flanks of the flanges 22 are formed by a pair of sheet-metal plates 3b and 30 whose lower edges are turned outwardly at 3d and 3e to rest approximately against the inner surfaces of the walls 20 and 2b of the mold. Hence a full-height flange may be cast within the space defined between the inner and outer shells 2 and 3, respectively.

The vertical height of the flanges 22 can, in accordance with the structural requirements, be adjusted by the use of vertically shiftable strips 4 which are shown to be of angle profile and comprise a horizontal leg 4a and a vertical leg 4b, the latter being adjustably fixed to the walls 3!) and 3c by screws 4c. Hence it is possible to lift the leg 4a from its solid-line position there illustrated and shorten the height of the flange 22 to be formed.

According to an important feature of this invention, strips 28, with anchoring pins, studs or projections 28a extending upwardly, can be placed upon the members 4 to be locked into the concrete body in the manner of the strips 36 illustrated in FIG. 2. Strips 28 can be composed of a material to which underlying plates may be connected with screws or the like. It is also possible to mount studs, nuts, screws or like fastening means upon the members 4 for embedding in the concrete or to use wire loops for this purpose.

At places corresponding to the openings 23, 24 etc., the mold is provided with plates of cellular polystyrene, wood or other material readily removable from the concrete body after hardening thereof. As noted earlier, an important aspect of the present invention resides in the removal of the partially hardened and incompletely set concrete from the outer shell 1 of the mold together with the inner shell or form 3. We prefer, if this procedure is followed, to cut the openings 23 and 24 in the soft concrete.

It has been found to be convenient, moreover, to produce a number of concrete elements 20 in a single mold. In this case, templates 5 (FIGS. 5, 6 and 10) are provided at spaced locations along the mold, these templates having the configuration of the desired concrete element and, therefore, the configuration of the mold cavity. Between each pair of elements 5, a respective structuralelement 20 is produced. Of course, when each of the structural elements is to extend over no more than half the length of the mold, two or more concrete bodies may be produced within the mold.

As best seen in FIGS. 6 and 10, the spacer templates 5, which define the extremities of the individual structural elements manufactured in a particular mold and also may serve as a gauge for proper setting of the inner form 3, can comprise a bar 5a having a pair of legs 5b and 5c and thereby corresponding to an inverted U. The bars and legs may be provided with openings 13 traversable by reinforcing rods extending through the mold cavity so that the templates simultaneously serve as supports and spacers for these reinforcing rods. Moreover, the template 5 has C-clamp 11 with an arm 11a overhanging the leg 5c and defining a throat 11b into which the wall 2b of the outer form can extend. The template 5 can be tightened in place by a pair of thumb screws 12 traversing the arm 11a. To prevent canting of the template within the mold cavity, we provide the template with a bracket 6 having legs 6a and 6b which rest upon the edge 20 previously described. Since the template 5 also determines the angle of the end face of each structural element and it may be desired to have this end face include an angle with the platform surface which is other than 90, we provide the template 5 with a surface 5e inclined at the desired angle D to the horizontal (see FIG. 10). To adjust the leg of the individual structural elements, therefore, it is merely necessary to loosen the screws 12 and shift the template 5 to the desired position along the trough formed by the outer shell 2 of the mold. The various movable parts of the inner form amy then be adjusted to rest against the inner periphery 5d of the templates, thereby accuratly establishing the dimensions and configuration of the cast body. Reinforcing members can then be inserted through the openings 13 and concrete cast between each pair of templates. The strike board is drawn across the edges 2c of the lateral walls of the mold to smooth the upper surface of the cast body which is permitted to harden until its slump is negligible. Prior to the establishment of a self-supporting state of the concrete and after decline of its slump to zero, the inner form is lifted out of the outer form together with the nonsupporting cast concrete bodies and carried to a hardening station at which a hot fluid, e.g., steam or hot air, is conducted through the interiors of the inner form and, if desired, through the pipes 9. Since a number of such inner forms and hardening bodies will generally be provided at this station because of repeated use of the outer form for the casting of further bodies, the inner forms may be connected in series or parallel to conduct the heated fluid through them. When each of the bodies has hardened, set or cured sufficiently to be self-supporting, the inner form may be turned over to permit the concrete body to rest on its platform-forming surface and the inner form to be lifted therefrom by the crane. Prior to setting or hardening of the body, openings may be cut into the soft concrete as noted earlier, and after hardening and opening-forming inserts may be knocked out as desired. Upon erection of the laterally contiguous bodies into a platform, these openings can be closed. Unused openings 13 in the template 5 may be closed by plugs.

In FIG. 9, we have shown somewhat diagrammatically a mold for the formation of concrete bodies wherein a pair of lateral walls 102a and l02b on supports 10] define the outer form. The inner forms 1030, 103b and 103C are here shown to be located behind an end plate 10 and to be constituted of sheet metal as shown in FIG. 5 or of concrete as previously described. Conduits 9 may traverse the inner forms to secure them to the end plates 10, the end plate having a wire loop 10a enabling the inner forms and the concrete body carried thereby to be lifted from the mold. The conduits 9 may serve merely to attach the inner forms to the end plates 10 or also as conduits for the introduction of steam or other heating medium into these forms. The assembly illustrated in FIG. 9 is used to produce a I l-shaped body as represented in broken lines, the flanks of its flanges 122 converging downwardly while the spaces defined between these flanks and the respective web 121 form trapezoids with the broad base atthe bottom...

When the mold illustrated in FIG. 9 is used, the templates must have a corresponding tr-shaped configuration. It is also possible to insert the templates into the reinforcement basket when the latter is constructed outside the mold for insertion together with the reinforcements into the latter.

In FIG. 7, we have shown a strike board 15 having shoulders 15a adapted to ride upon the edges 2c of the mold and a central tongue 15b extending within the mold cavity for establishing the thickness of the web of the concrete body. In FIGS. 3 and 4, we have also shown that the exterior of the mold is provided with vibrators 8 for compacting and jolting the concrete. To facilitate removal of the cast concrete bodies from the inner and outer form, the latter may be oiled as is conventional with concrete formwork or provided with a synthetic-resin coating having low adhesion to the concrete. In FIG. 8, we show a negative form 16 for the of the sheet-metal inner form illustrated in FIGS. and v 9. Conduit means may be provided within these concrete inner forms as shown at 16a to conduct a heating medium through the body to promote curing of the concrete. When it is desired to provide inner forms of different height, as when the flanges of the structural elements are to have different heights, one need only employ a negative form of a depth corresponding to the height of the largest inner form to be made and cast the inner forms to the required depth of concrete. The negative form, as will be apparent, is of trapezoidal configuration.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

We claim:

l. A mold for the production of an elongated concrete structural element having a web adapted to form part of a platform surface upon the assembly of a number of such elements in laterally contiguous relationship, and a pair of flanges adapted to extend downwardly from the web and unitarily therewith, said mold comprising:

a trough-shaped outer form havinga pair of transversely spaced longitudinally extending vertical walls running at least the length of one of said elements; I

at least one inner form removably received between said walls and defining a mold cavity therewith having a pair of downwardly extending compartments adapted to form said flanges upon the casting of concrete in said cavity, said inner form being removable from said outer form together with a concrete body cast thereon;

vibrating means mounted on said outer form;

a pair of end plates closing opposite extremities of said cavity and secured to said inner form for re moval therewith, said end plates being provided with means engageable by a crane to enable the lifting of said inner form and a concrete body carried thereby from said outer form; and at least one spacer template disposed insaid cavity and having a configuration substantially identical to the crosssection of said element and adjustably mounted on one of said walls for defining the length of an element cast in said cavity.

2. A mold for the production of an elongated concrete structural element having a web adapted to form part of a platform surface upon the assembly of a number of such elements in laterally contiguous relationship, and a pair of flanges adapted to extend downwardly from the web and unitarily therewith, said mold comprising:

a trough-shaped outer form having a pair of transversely spaced longitudinally extending vertical walls running at least the length of one of said elemcnts;

at least one inner form removably received between said walls and defining a mold cavity therewith having a pair of downwardly extending compartments adapted to form said flanges upon the casting of concrete in said cavity, said inner form being removable from said outer form together with a concrete body cast thereon; and

at least one spacer template disposed in said cavity and having a configuration substantially identical to the cross-section of said element and adjustably mounted on one of said walls for defining the length of an'element cast in said cavity.

3. The mold defined in claim 2 wherein the spacer template is provided with a plurality of openings traversible by reinforcements to be embedded in the concrete body.

4. The mold defined in claim 3, further comprising a bracket engageable with the upper edge of said one of said walls and provided on said template for positioning same with a surface in a desired angular relationship within said mold.

5. The mold defined in claim 2, further comprising adjustable means in said compartments for setting the bottoms thereof an thereby defining the heights of said flanges.

6. The mold defined in claim 5, further comprising means enabling transverse movement of at least one of said walls relative to the other of said walls to establish the width of the element cast in said mold.

7. The mold defined in claim 6, further comprising a strike board adapted to be drawn along the upper edges of said walls and extending partly into said cavity to define the thickness of said web.

8. The mold defined in claim 6, further comprising means in said inner form for passing a heating medium therethrough.

9. The mold defined in claim 8 wherein said cavity has a uniform curvature in the longitudinal direction for imprating an annular curvature to said element.

10. The mold defined in claim 2, further comprising vibrating means mounted on said outer form. 

1. A mold for the production of an elongated concrete structural element having a web adapted to form part of a platform surface upon the assembly of a number of such elements in laterally contiguous relationship, and a pair of flanges adapted to extend downwardly from the web and unitarily therewith, said mold comprising: a trough-shaped outer form having a pair of transversely spaced longitudinally extending vertical walls running at least the length of one of said elements; at least one inner form removably received between said walls and defining a mold cavity therewith having a pair of downwardly extending compartments adapted to form said flanges upon the casting of concrete in said cavity, said inner form being removable from said outer form together with a concrete body cast thereon; vibrating means mounted on said outer form; a pair of end plates closing opposite extremities of said cavity and secured to said inner form for removal therewith, said end plates being provided with means engageable by a crane to enable the lifting of said inner form and a concrete body carried thereby from said outer form; and at least one spacer template disposed in said cavity and having a configuration substantially identical to the cross-section of said element and adjustably mounted on one of said walls for defining the length of an element cast in said cavity.
 2. A mold for the production of an elongated concrete structural element having a web adapted to form part of a platform surface upon the assembly of a number of such elements in laterally contiguous relationship, and a pair of flanges adapted to extend downwardly from the web and unitarily therewith, said mold comprising: a trough-shaped outer form having a pair of transversely spaced longitudinally extending vertical walls running at least the length of one of said elements; at least one inner form removably received between said walls and defining a mold cavity therewith having a pair of downwardly extending compartments adapted to form said flanges upon the casting of concrete in said cavity, said inner form being removable from said outer form together with a concrete body cast thereon; and at least one spacer template disposed in said cavity and having a configuration substantially identical to the cross-section of said element and adjustably mounted on one of said walls for defining the length of an element cast in said cavity.
 3. The mold defined in claim 2 wherein the spacer template is provided with a plurality of openings traversible by reinforcements to be embedded in the concrete body.
 4. The mold defined in claim 3, further comprising a bracket engageable with the upper edge of said one of said walls and provided on said template for positioning same with a surface in a desired angular relationship within said mold.
 5. The mold defined in claim 2, further comprising adjustable means in said compartments for setting the bottoms thereof an thereby defining the heights of said flanges.
 6. The mold defined in claim 5, further comprising means enabling transverse movement of at least one of said walls relative to the other of said walls to establish the width of the element cast in said mold.
 7. The mold defined in claim 6, further comprising a strike board adapted to be drawn along the upper edges of said walls and extending partly into said cavity to define the thickness of said web.
 8. The mold defined in claim 6, further comprising means in said inner form for passing a heating medium therethrough.
 9. The mold defined in claim 8 wherein said cavity has a uniform curvature in the longitudinal direction for imparting an annular curvature to said element.
 10. The mold defined in claim 2, further comprising vibrating means mounted on said outer form. 